MineralsPurgativeNatrii Sulfas

Mang Xiao (Mirabilite / Glauber's Salt)

A practical guide to Mang Xiao: what it is, how Traditional Chinese Medicine uses it, the classical formulas it appears in, and who should be careful with it.

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Last reviewed Oct 13, 2026

Quick Facts

Latin NameNatrii Sulfas
Chinese Name & Pinyin 芒硝 · Mang Xiao
Medicinal PartMinerals
The herbMang Xiao is refined hydrous sodium sulfate crystals. Xuan Ming Fen and Pu Xiao are different grades. Magnesium sulfate is not this drug.
Nature and channelsSalty, bitter, cold. Enters the Stomach and Large Intestine. Saltiness softens hardness. Bitter cold drains heat.
Pharmacopoeia lineDrains downward and attacks accumulation. Moistens dryness and softens hardness. Clears heat and reduces swelling. Used for excess-heat accumulation, abdominal fullness and pain, dry bound stool, and intestinal abscess; externally for breast welling-abscess and swollen hemorrhoids.
Pattern cuesAbdominal fullness that refuses pressure. Dry bound constipation. Intestinal abscess. Dry yellow coating. Full pulse.
In this articleMang Xiao versus Xuan Ming Fen, Da Huang, and Epsom salt. Why it is dissolved, not boiled. Why pregnancy is a stop sign. Who should skip it.

What Is Mang Xiao?

Mang Xiao (芒硝; Máng Xiāo; Latin: Natrii Sulfas; English: sodium sulfate / Glauber’s salt) is the refined crystalline mineral from the mirabilite group, mainly hydrous sodium sulfate. In Chinese medicine it is a draining, precipitating herb. It is salty, bitter, and cold, enters the Stomach and Large Intestine channels, and its core actions are to drain downward and attack accumulation, moisten dryness and soften hardness, and clear heat and reduce swelling. In a decoction it is usually dissolved and taken as a draft, not boiled for a long time. It is not Xuan Ming Fen, the weathered dried form, which purges more gently. It is not Epsom salt (magnesium sulfate). The chemistry is different. They are not interchangeable. Pu Xiao is the crude mineral and must be refined before internal use.

It is used most often for three patterns:

  • Excess-heat accumulation with dry bound stool — abdominal fullness and pain, no bowel movement
  • Intestinal abscess with swelling and pain — interior excess heat-toxin
  • External use for breast welling-abscess and swollen hemorrhoids — clearing heat and reducing swelling

The usual dose, dissolved, is 6–12 g. Avoid in pregnancy. A cold weak spleen and stomach, or elderly fluid deficiency with no excess-heat accumulation, is a poor match. Salty-cold softening and purging is not a home constipation powder to repeat on your own.

In Yangming fu excess, when heat binds and dry stool sits, fullness that refuses pressure is common. Mang Xiao is salty-cold and moistens while it drains. It is the partner of Da Huang in Da Cheng Qi Tang. It attacks more than it supports. Cold-type constipation in a weak middle collapses further if more purging is added.

Mang Xiao is not a catch-all laxative, and it is not a do-it-yourself “detox salt.” In deficiency-cold constipation or dry stool with no excess accumulation, using it alone easily injures upright qi and the stomach. Whether to purge, and at what dissolved dose, should be decided by a licensed Chinese medicine practitioner after pattern diagnosis.

Mang Xiao Mirabilite

Mang Xiao: Materia Medica Profile

Identification & Quality Standard

Natrii Sulfas

Botanical Origin

The refined crystals made from mirabilite, primarily consisting of Na2SO4•10H2O.

Production Regions

Produced in most areas of China.

Quality Requirements

Superior medicinal material has crystal lumps, colorless translucent color.

Macroscopic Features

Single crystal system, crystal is short cylindrical or needle-like; often in dense lumps or fiber-like clusters. Colorless or white, glass-like and lustrous, intact surface cleavage, 1.5~2 mohs hardness, density 1.48. Tastes clear and cool, slightly bitter and salty, very easily becomes liquid after absorbing moisture; in dry air, it gradually loses water to become anhydrous mang xiao. Ridged-cylindrical, rectangular or irregular lumps and granules. Colorless translucent or off-white translucent. Brittle texture, easily crushed, fractured surface is spotted and lustrous. faint odor, salty taste.

Origin and Quality Identification

Traditionally, the best quality comes from regions like Shanxi, Hebei, and Inner Mongolia, though the final quality heavily depends on the season and processing methods.

  • Identifying Premium Quality: Good raw Mang Xiao appears as colorless, transparent, or semi-transparent crystals. It should be brittle with a glass-like shine, and have a salty, slightly bitter taste.
  • Processed Looks: Xuan Ming Fen is a loose, white powder, whereas raw crystals are harder and slightly darker.
  • Common Imposters: It is sometimes confused with other minerals like saltpeter. A quick traditional test is to burn it: saltpeter produces a purple flame, while Mang Xiao does not.

Traditional Properties & Historical Lineage

Nature, Flavour & Channel Tropism

Salty, Bitter; ColdStomachLarge Intestine

1. Historical Records

  • Shen Nong Ben Cao Jing (Classic of the Materia Medica): Listed it as a lower-tier remedy, noting its ability to clear deep-seated heat in the organs, relieve stomach bloating, and flush out accumulated food.
  • Ben Cao Gang Mu (Compendium of Materia Medica): Confirmed its strong purgative effects for resolving constipation, draining excess fluids, and even treating skin swellings externally.
  • De Pei Ben Cao (Materia Medica of Combinations): Highlighted its famous pairing with Da Huang (Rhubarb) to treat severe intestinal heat marked by high fever and delirium.

2. Evolution of TCM Understanding

Throughout history, the medical view of Mang Xiao has shifted. Early texts focused on its ability to aggressively clear gut stagnation. Later doctors emphasized its unique "softening" property for resolving hard masses. TCM masters eventually realized that because of its strong cold and downward nature, it should rarely be used alone. It is usually paired with other herbs to protect the body's vital energy. By the Ming dynasty, its external use for clearing heat and reducing swelling in skin conditions became highly valued.

Mang Xiao Mirabilite

Core Efficacies & Traditional Applications

Traditional Functions

Breaks distention, warms middle, digests food, drains water, moderates diarrhea. Apply to abdominal fullness, food retention, indigestion, edema, mammary swelling, amenorrhea, constipation.

1. Primary Focus: Purging Heat and Relieving Constipation

Mang Xiao (Glauber's Salt) is traditionally used as a strong purgative to clear internal heat and flush out severe accumulation in the stomach and intestines.

  • Common Indications: It is highly effective for "excess heat" constipation, marked by very dry, hard stools, severe abdominal bloating and pain, bad breath, and a thick yellow tongue coating.
  • Common Pairings: Because of its specific action, it is rarely used alone for digestion. It is typically paired with Da Huang (Rhubarb) and Zhi Shi (Immature Bitter Orange) to synergistically soften stools and stimulate bowel movements.
  • When to Avoid: If you have a weak or "cold" digestive system, or if you are elderly and physically frail, do not use this on your own. It can severely damage your body's warming energy (Yang) and worsen digestive weakness.

2. Secondary Focus: Clearing Heat and Reducing Swelling

Externally, its cold and salty nature helps "soften" and dissipate localized heat, swelling, and hard nodules.

  • Common Indications: It is traditionally used for red and swollen eyes, sore throats, skin sores, and breast abscesses where the tissue is red, hot, swollen, and hard.
  • Common Pairings: For external application, it is often powdered and mixed with herbs like Da Huang (Rhubarb) and Zhi Zi (Cape Jasmine Fruit) to create a cooling poultice.
  • When to Avoid: Do not apply this mineral to broken skin or open wounds, as it will cause irritation and potentially worsen the infection.

3. Common Herb Pairings

The most famous pairing is Mang Xiao (Glauber's Salt) and Da Huang (Rhubarb).

  • Da Huang is bitter and cold; it aggressively purges heat and moves stagnation.
  • Mang Xiao is salty and cold; it specifically softens dry, rock-hard stools. Together, they provide a powerful one-two punch for severe intestinal heat and stubborn constipation. However, this is a potent medical combination that easily causes over-purging and must only be used under a practitioner's guidance.
Mang Xiao Mirabilite

Modern Research

Modern research offers useful context, but Traditional Chinese Medicine prescribes on whole-pattern diagnosis rather than isolated compounds.

1. Key Chemical Components

Modern chemical analysis confirms that Mang Xiao (Glauber's Salt) is almost entirely sodium sulfate, with trace amounts of sodium chloride, magnesium sulfate, and calcium sulfate.

  • Lab Observations: In test tubes and animal models, sodium sulfate increases the osmotic pressure in the intestines. This draws water into the gut, softening stool and triggering bowel movements.
  • Human Studies: Small clinical observations confirm that standard doses increase bowel movement frequency, aligning with its traditional use as a laxative.

2. Modern Pharmacological Directions

Today, Western scientific research on this mineral focuses mainly on its laxative mechanism (osmotic regulation) and its potential for external anti-inflammatory and swelling-reduction effects. However, most of these modern studies are limited to lab cells and animals, requiring more human trials to confirm clinical applications.

3. Limitations of Modern Research

  • Lab vs. Real Life: An isolated chemical reaction in a lab does not fully represent how the human digestive system processes the mineral.
  • Single Chemicals vs. Traditional Use: Modern labs often test pure sodium sulfate. This is very different from traditional TCM decoctions, which use specific doses and preparation methods (like boiling with radish) to alter the mineral's harshness.
  • Varying Standards: Different studies use different extraction methods and doses, making it hard to create a unified scientific consensus.
  • Holistic Synergy: TCM views healing as a systemic balance. Focusing purely on the "sodium sulfate" laxative effect ignores how the mineral interacts with other herbs in a prescribed formula to treat complex heat patterns.
Mang Xiao Mirabilite

Comparing Similar Herbs

1. Shared Traits with Similar Herbs

Mang Xiao (Glauber's Salt) is constantly compared to Da Huang (Rhubarb).

  • Both are powerful purgatives that clear out intestinal blockages.
  • Both treat severe heat stagnation in the gut (bloating, constipation, abdominal pain).
  • Both are strictly contraindicated for people with a cold or weak spleen and stomach.

2. Core Differences

  • Nature and Flavor: Mang Xiao is salty, which gives it a unique "softening" property to break down hard masses. Da Huang is bitter, focusing more on aggressively draining heat and moving blood.
  • Focus of Action: Mang Xiao is the specialist for softening rock-hard stool and localized hard swellings. Da Huang acts more broadly to clear systemic heat (like upper body fire) and improve blood circulation.
  • Clinical Indications: Choose Mang Xiao when the primary issue is extremely dry, pebble-like stool or hard, hot surface swellings. Choose Da Huang if the constipation is paired with bleeding gums, severe bad breath, or blood stasis issues.

3. A One-Sentence Summary

Mang Xiao (Glauber's Salt) excels at softening hard stool and clearing gut accumulation, whereas Da Huang (Rhubarb) is better at broadly purging systemic fire and moving stagnant blood.

Mang Xiao Mirabilite

Classical Formulas Containing Mang Xiao

+2 more

Formulas vs. Single Herbs

  • Synergy is Key: A formula is a balanced team. The healing power comes from how the herbs interact, so a single herb cannot simply replicate a full formula's effects.
  • Holistic Balance: The exact dosage and combination in a formula affect the entire body. Never try to mix or alter these formulas at home based on internet articles.

Diet & Daily Home Use

1. Home Herbal Uses

Because this is a strong purgative, internal home use is not recommended. However, a low-risk external application can be used for mild bloating:

  • Radish and Mang Xiao Compress:
    • Ingredients: 10g Mang Xiao (Glauber's Salt), 50g fresh white radish.
    • Method: Boil the sliced radish until soft, extract about 50ml of the juice, and stir in the Mang Xiao until dissolved. Soak a gauze pad in the liquid and apply it to the navel area for 15-20 minutes, once a day.
    • Best For: Mild abdominal bloating with slight constipation (without severe pain).
    • Not For: People with a cold stomach, skin allergies, or broken skin around the navel. Use strictly no more than twice a week.

2. Processing Differences and Preparation

  • Raw vs. Processed: Raw Mang Xiao is hard and intensely cold. The dehydrated powder form, Xuan Ming Fen, is slightly milder and less irritating to the stomach.
  • Brewing Rule: Never boil Mang Xiao. Because it is a highly soluble mineral salt, boiling destroys its properties. Instead, you boil your other herbs first, strain the liquid, and then dissolve the Mang Xiao directly into the warm herbal tea.
  • Dosage Conversion: Doses do not translate directly between forms. If a recipe calls for the raw mineral, replacing it with the dehydrated powder requires reducing the dose by about one-third.

3. Dosage and Usage Cycle

  • Dosage: Traditional clinical doses range from 3g to 10g. For external home use, keep it under 10g. Do not ingest it for daily dietary therapy.
  • Cycle: This is a fast-acting, short-term remedy. Do not use it for more than 3 consecutive days. If symptoms persist, consult a doctor immediately.
Mang Xiao Mirabilite

Contraindications & Safety Warnings

1. Who Should Avoid It

  • Cold Constitutions: If you have a weak, cold digestive system (frequent loose stools, a preference for warm drinks, cold hands and feet), strictly avoid this mineral.
  • Pregnancy and Nursing: It is strictly forbidden for pregnant and breastfeeding women, as its strong downward, purging action can be harmful.
  • Special Populations: Children and the elderly have weaker digestive systems and should only use this under strict medical supervision.
  • Organ Dysfunction: People with liver or kidney issues, or those allergic to sulfates, must avoid using it.

2. Drug Interactions and Dietary Notes

  • Medication Interactions: Its strong osmotic effect in the gut can interfere with how your body absorbs oral medications, such as antibiotics, blood pressure drugs, and blood sugar regulators. Always separate it from Western medications by at least 1-2 hours.
  • Blood Thinners: It may theoretically increase bleeding risks if combined with anticoagulant medications. Always ask your pharmacist before combining treatments.

3. Adverse Reactions and Overdose Risks

  • Digestive Upset: Taking too much internally will cause severe diarrhea, stomach cramps, nausea, and vomiting, leading to dangerous dehydration.
  • External Reactions: When used topically, it can sometimes cause skin redness, itching, or allergic rashes.
  • Emergency: If you experience continuous vomiting, breathing difficulties, extreme weakness from diarrhea, or a sudden worsening of your condition, stop using it immediately and seek emergency medical care.

Frequently Asked Questions About Mang Xiao

What is Mang Xiao? Are Pu Xiao, Pi Xiao and Xuan Ming Fen the same?
Official Mang Xiao (芒硝) is refined sulfate mineral crystals, mainly sodium sulfate decahydrate (Na2SO4·10H2O). The pharmacopoeial name is Natrii Sulfas. Pu Xiao / Pi Xiao hold more impurities and are mostly external, not for internal use. Xuan Ming Fen (weathered nitre) is anhydrous sodium sulfate from weathering Mang Xiao—gentler, 3–9 g internally, also used on mucosa. Do not swap in industrial thenardite or saltpeter (potassium nitrate). Write Mang Xiao or Xuan Ming Fen, dissolve it, and do not boil it long.
What are the TCM properties and traditional uses of Mang Xiao?
According to the Chinese Pharmacopoeia, Mang Xiao is salty, bitter and cold, enters the Stomach and Large Intestine channels, and acts to drain downward and unblock the bowels, moisten dryness and soften hardness, and clear fire to reduce swelling. It is used for excess-heat accumulation, dry bound stool and abdominal fullness with distending pain; externally for swollen painful throat, mouth sores, red eyes, abscesses, erysipelas, breast carbuncle and swollen hemorrhoids. Salty-cold softening—suited to dry stool with heat bind, not to Spleen-Stomach deficient cold or patterns without excess-heat dry bind.
Why dissolve Mang Xiao rather than decoct it? How do you choose Xuan Ming Fen?
Long boiling decomposes sodium sulfate and irritates the gut; the pharmacopoeia requires it to be dissolved into the finished decoction, not cooked with the other herbs. Excess-heat dry bind uses 6–12 g Mang Xiao; upper-jiao heat swelling, mucosal use or a gentler force uses Xuan Ming Fen. Breast carbuncle and swollen hemorrhoids may be packed with Pu Xiao or Mang Xiao. Store sealed below 30 °C so it does not weather to powder.
What is the usual dosage? Can it be used daily to unblock the bowels?
The pharmacopoeial internal dose is 6–12 g dissolved into the decoction; external use as appropriate. Xuan Ming Fen internally is 3–9 g. It is not a daily “saline laxative tea.” Deficient-cold loose stool and elderly fluid depletion without heat bind grow more damaged. Excess-heat dry bind needs a short course with rhubarb, stopped once the bowels move.
What are the contraindications? Can it be used in pregnancy?
Forbidden in pregnancy; avoid in Spleen-Stomach deficient cold. Salty-cold draining can abort and injure Yang. Use caution in menstruation, postpartum and lactation; packing the breast may return milk. Do not combine with sulfur or Sparganium. Excess can dehydrate and disturb electrolytes. Stop and seek care if severe abdominal pain or collapse appears.
Can Mang Xiao unblock the bowels, soften hardness and reduce swelling?
It can help excess-heat dry bind. Yangming fu excess joins rhubarb, unripe bitter orange and Magnolia bark in Da Cheng Qi Tang; dryness-heat constipation joins rhubarb and licorice in Tiao Wei Cheng Qi Tang. Pack early breast carbuncle and swollen hemorrhoids. It drains heat-bound dry stool—not a specific for every constipation, every appendicitis or every mastitis. Acute abdomen and high fever with a hard belly are emergencies.
Can Mang Xiao be taken daily as a detox, slimming or laxative salt?
No. It is an osmotic saline purgative, only for short courses of excess-heat dry bind. “Mirabilite detoxes and slims” does not replace gastroenterology and weight care. Industrial sodium sulfate must not be swallowed. Draining downward and softening hardness should name Mang Xiao or Xuan Ming Fen and a dissolved dose.
How do you choose among Mang Xiao, Da Huang, Fan Xie Ye, Huo Ma Ren and Xuan Ming Fen?
Mirabilite is salty-bitter-cold: moistens dryness, softens hardness and drains heat to unblock the bowels—dissolved, not boiled long. Rhubarb is bitter-cold: drains downward, attacks accumulation, clears heat and fire, moves Blood and resolves toxin—added late. Senna is sweet-bitter-cold: drains heat to unblock the bowels, fierce as an infusion. Hemp seed is sweet-neutral: moistens the intestine, suited to fluid depletion and intestinal dryness. Xuan Ming Fen is weathered Mang Xiao, gentler. Dry hard stool favors Mang Xiao with rhubarb; heat bind without dryness may use rhubarb alone; deficient constipation favors hemp seed. Rhubarb and Mang Xiao are often paired; all are forbidden when there is deficient cold and no bind.
Which herbs is Mang Xiao combined with? What are the representative formulas?
Yangming fu excess with glomus, fullness, dryness and excess joins rhubarb, unripe bitter orange and Magnolia bark in Da Cheng Qi Tang. Dryness-heat constipation joins rhubarb and licorice in Tiao Wei Cheng Qi Tang. Write that it is dissolved; do not combine with sulfur or Sparganium. Externally for breast carbuncle and hemorrhoids it may stand alone or join rhubarb and borneol.
How do you choose and store Mang Xiao?
Choose colorless or white prismatic crystals with a glassy fracture and a salty-bitter taste. Yellow-red impurities, lots that have deliquesced to paste, and anonymous industrial salt are unused. Seal below 30 °C against weathering. Buy medicinal Mang Xiao or Xuan Ming Fen; do not swallow saltpeter, Pi Xiao internally, or industrial thenardite.

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Medical Disclaimer — This article is provided for educational purposes only and describes traditional Chinese medicine concepts. It is not medical advice, and it is not intended to diagnose, treat, cure or prevent any disease. Always consult a qualified practitioner before using any herb, particularly if you are pregnant, nursing, taking medication or managing a diagnosed condition.

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Mang Xiao (Mirabilite): Drain Downward, Moisten Dryness, and Soften Hardness